This project is designed to evaluate the nature of lactogenic hormone receptors and the factors (including other hormones) which affect binding of the hormone to this molecule. Studies include 1) purification of the receptor from human tissue and preparation and characterization of an antibody against it; 2) examination of the nature of the subunits of the receptor, 3) characterization of the nature of the interaction of Tamoxifen with membrane bound receptors related to the lactogen receptor, and 4) define the relationship of monoclonal antibody B6.2 to human lactogenic hormone receptors.